1. Field of the Invention
The present invention relates to an ink jet recording apparatus having the functions of a facsimile, copying machine, printer and the like, or usable as an output apparatus for composite equipment, a work station and the like having such functions.
Also the present invention relates particularly to an ink jet recording apparatus having, as recording means, a so-called ink jet recording head of a full-line type having a recording width corresponding to the maximum recording width of a recording medium, or having a plurality of such recording heads for black ink or for inks of respectively different colors.
2. Related Background Art
Non-impact recording methods are recently attracting attention due to their advantage that the noise level during recording is negligible. Among these methods, ink jet recording is particularly promising because it can perform high speed recording on ordinary paper without particular fixing treatments.
The recording head employed in an ink jet recording apparatus is generally provided with a small liquid discharge port (orifice), a liquid path, an energy applying part formed in said liquid path, and energy generating means for generating energy, for liquid droplet formation, to be applied to the liquid present in said energy applying part.
For such energy generating means there are known an electromechanical converting member, such as a piezoelectric element; irradiation with an electromagnetic wave, such as a laser beam, which is absorbed in the liquid and generates heat therein for generating and discharging a liquid droplet; and an electrothermal converting element such as a heat-generating resistor for heating the liquid thereby discharging a liquid droplet. Among these, a recording head for causing liquid droplet discharge by thermal energy has various advantages as disclosed in U.S. Pat. Nos. 4,740,796 and 4,723,129.
In contrast to the so-called serial scanning recording method in which the printing is conducted by reciprocating motion of the recording head on a stationary recording sheet, U.S. Pat. No. 4,692,778 discloses a fixed recording head consisting of an array of plural recording heads and enabling full-line printing. That patent discloses various apparatus, many of which are already reduced to practice.
However a full-line recording head obtained by combining plural recording heads is expensive, and a complex structure is required for the positioning of each head. Also the entire recording head becomes inevitably bulky if plural full-line recording heads are employed.
Numerous designs have been made of a full-line recording head consisting of a long single head for satisfying the requirements of compactization of the apparatus, stable image formation and high speed recording, but it has not been possible, in any design so far, to avoid drawbacks related to recovering the discharge function of the recording head.
When, the recording head is defined as a multi-nozzle type and made with the same width as the recording sheet, such a recording system is quite different from prior serial scan systems. Thus, various and different problems occur not encountered in prior serial scan systems.
In a multi-nozzle system, recording speed can be greatly increased as compared with a serial scan system. However, when printing on an OHP (over-head projector) paper into which ink is absorbed slowly, ink is not fixed or dried in a desired manner, and when ink is superimposed by color printing or the like, ink tends to overflow or cause blurring.
Additionally, when recording or exhausting at high speed a non-coated sheet without a coating agent, such as the OHP paper and PPC (plain-paper copier) paper used in an electrophotographic copying machine, both of which have low water absorption properties, ink may not be fully dried when the sheet is exhausted, thus causing offset of the sheet in the exhausting section and staining of on the back of the sheets.